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Wednesday, April 20, 2011

Here's one item of concern from the latest Tepco report

Continuity will become a challenge, and core Fukushima staff may have to be cycled out soon to due dose limit considerations

If you're not already familiar with the number, 250 milliSieverts is the absolute yearly dose limit for staff working emergency cases at the Fukushima Dai-ichi nuclear site. The percentage of workers who are quickly approaching this dose limit remains a mystery, but a look at Tepco's data helps us understand that a good amount of their early-responders (undoubtedly their most valuable staff) will easily hit their limits within a few months.

Based on the chart above, readings at the west gate (at a considerable distance from all the action) are slowly declining but are still at a hot 50 microSievert per hour. At 50μSv/hr (0.05mSv/hr), an employee at this location will rack up enough dose to hit their annual limit in just 208 days.

Where else can these guys hang out during idle time like after they've finished spraying kuricoat or after running a packbot mission? Sure as hell not at the site boundry - as of 4/15, it was registering a smokin 12 milliSievert/hr, taking any employee out of the system in just 21 hours time.

The shortest tenure in all the history of nuclear employment comes by way of reactor 3 and its vicinity, where a whopping 400milliSievert/hr dose rate will max you out in just 37.5 minutes. Break your leg at this location beyond earshot of anyone and you will face certain death after just 17.5 hours of exposure.

This is why Tepco currently has 700 people working the plant. The situation necessitates constant ojt/cross-training, because skilled workers in the trenches there can't possibly remain for sustainable periods of time. If you have nuclear work experience, are a notorious job-hopper and have absolutely no interest in having kids, this is the perfect job for you. No disrespect meant for Fukushima employees - that's just how it is.

This raises another essential point: If employees can work near the reactors for only minutes at a time, how can the existing cooling systems be repaired? That effort requires cleaning, repairs, welding, installation of new parts and most importantly - hours and hours of continuous work in high dose areas. Judging from the wreck of what's leftover from the explosions, it ain't gonna happen.

4 comments
:

"It is worrying that data recently dug out of the EPA shows Uranium in High Volume Air Samplers in the Mariana Island, Hawaii, California. The data cover the last 2 weeks of March. There is a trend with distance from Japan. We have seen no data for Japan itself but infer that levels are very high. We have been predicting the existence of such a problem from the first moment it became apparent that the spent fuel ponds were compromised and we have deplored the lack of official data on alpha emitting radionuclides which are virtually impossible for ordinary people to detect. Lawsuits for reckless endangerment would be valid.Official advice will be that the doses from the Uranium will be minuscule and no threat to health. This opinion will be based on the conventional notion of "absorbed dose" which is now known to be invalid for this kind of exposure. External sources like cosmic rays and x-rays distribute their energy evenly, like the sun; others, notably alpha emitters like Plutonium and Uranium, are extremely uneven in the way they irradiate body tissue once they have been inhaled or swallowed. Alpha particles emitted from the decay of Uranium atoms are relatively massive. They slow down rapidly and thus deposit all their energy in a microscopic volume of tissue. Applying the "absorbed dose" quantity the sievert (the conventional "absorbed dose" quantity) to this pinpoint of internal radiation means considering it as if it were a dose to the whole body. It's an averaging error, akin to believing it makes no difference whether you sit by the fire to warm yourself or eat a lump of burning coal. The International Commission on Radiologocal Protection admit that this averaging anomaly exists and that it is significant, but perversely they adhere to "absorbed dose". The scale of the error can be huge. At the extreme, the whole body dose from a single alpha particle track is 0.000000000005milliSievert (mSv) but the single cell which is the actual target gets 500mSv. It is the dose to the cell that causes genetic damage and, potentially, disease."

llrc.org’s Richard Bramhall : "It is worrying that data recently dug out of the EPA shows Uranium in High Volume Air Samplers in the Mariana Island, Hawaii, California. The data cover the last 2 weeks of March. There is a trend with distance from Japan. We have seen no data for Japan itself but infer that levels are very high. We have been predicting the existence of such a problem from the first moment it became apparent that the spent fuel ponds were compromised and we have deplored the lack of official data on alpha emitting radionuclides which are virtually impossible for ordinary people to detect. Lawsuits for reckless endangerment would be valid.Official advice will be that the doses from the Uranium will be minuscule and no threat to health. This opinion will be based on the conventional notion of "absorbed dose" which is now known to be invalid for this kind of exposure. External sources like cosmic rays and x-rays distribute their energy evenly, like the sun; others, notably alpha emitters like Plutonium and Uranium, are extremely uneven in the way they irradiate body tissue once they have been inhaled or swallowed. Alpha particles emitted from the decay of Uranium atoms are relatively massive. They slow down rapidly and thus deposit all their energy in a microscopic volume of tissue. Applying the "absorbed dose" quantity the sievert (the conventional "absorbed dose" quantity) to this pinpoint of internal radiation means considering it as if it were a dose to the whole body. It's an averaging error, akin to believing it makes no difference whether you sit by the fire to warm yourself or eat a lump of burning coal. The International Commission on Radiologocal Protection admit that this averaging anomaly exists and that it is significant, but perversely they adhere to "absorbed dose". The scale of the error can be huge. At the extreme, the whole body dose from a single alpha particle track is 0.000000000005milliSievert (mSv) but the single cell which is the actual target gets 500mSv. It is the dose to the cell that causes genetic damage and, potentially, disease."

Hey no problem they are talking about increasing the emergency dose to 500 milli-sievert per year with an OK from the ICRP to bosst it to 1000 milli-sievert if their cushy jobs are threatened. That's why pencils come with erasers as we're coming to find out nuclear power isn't an exact science.

Came across that article and it confirmed my suspicions even further that these guys are near their max dose already. It also raises speculation about the amount of qualified workers... maybe they'll have more trouble passing the baton to follow up staff than they realized.